1. Field of the Invention
This invention relates to a recording apparatus that performs recording on a recording paper.
2. Related Background Art
With the recent development of information processing systems, a variety of recording apparatuses have been developed. Of the recording methods used for these apparatuses, there is a serial-type recording method such that recording is performed in the traveling process of a recording head.
The ink jet recording apparatus using this serial-type recording method is usually constituted as shown in FIG. 12. A carriage 51 having a recording head 50 is movably mounted onto a guide rail 52. At the back of this carriage 51, a timing belt 53 is fixed in parallel to the guide rail 52 so that the drive force of a motor 54 is transferred through the timing belt 53.
In actual recording, the aforementioned motor 54 rotates both forwardly and reversely so that the carriage 51 can be reciprocated in parallel to a platen 55. In association with this movement, ink is discharged selectively from the recording head 50, thereby enabling recording on the recording sheet or paper 56.
With the ink jet recording, it is necessary to constantly maintain the space interval between an orifice surface of the recording head 50 (a discharge port surface) and the recording paper 56. As shown in FIG. 14, according to the conventional constitution used for maintaining the space interval at a constant, the carriage 51 is mounted movable along the axis of the guide rail 52 with its front end 51a contacted with a sheet pressing member 58, which is pressing the recording paper 56 against the friction roller 57 with the weight of the carriage 51.
With the carriage front end 51a in contact with the sheet pressing member 58, the carriage 51 travels along the guide rail 52, thus allowing a uniform space interval between the orifice surface of the recording head 50 and the recording paper 56 to be maintained.
However, in the above-mentioned constitution, a biasing force for biasing the front end of the carriage 51 against the paper pressing plate 58 is generated only by the weight of both carriage 51 and the recording head 50 mounted thereon. This causes the timing belt 53 to vibrate, for example when the carriage 51 reverses its traveling direction. The carriage 51 is liable to be effected by the vibration. This vibration on the part of the timing belt 53 will cause the carriage 51 to also vibrate as indicated by the arrow B in FIG. 14. This changes the uniform space interval between the orifice surface and the recording paper 56, so that recording may be performed in a waving state.
Furthermore, to raise the recording speed with regard to the reversed motion of the carriage 51, it is necessary to shorten the reversing time. In addition, both the timing belt 53 and the carriage 51 receive stronger impacts, causing recorded images to become more wavy.
In the recording apparatus, the transport roller 57 is not a single roller, but the transport roller 57 consists of a number of axially separated rollers mounted on the roller axis as illustrated in FIG. 12. This is for cost reduction by reducing the amount of rubber material constituting the transport roller 57 as well as for reducing of the weight of the apparatus.
As illustrated in FIG. 15, when the contact portion 51a of the carriage is pressed between adjacent transport rollers 57, the sheet pressing member 58 is slightly flexed inwardly toward the transport rollers 57. With the carriage 51 moving while it is in contact with the flexed sheet pressing member 58, the carriage 51 traces the curved profile of the sheet pressing member 58 and rocks around the guide rail 52 in the direction indicated by arrow B in FIG. 14.
Thus, the space interval between the carriage 51 and the recording paper 56 is not constant, causing recorded images to be wavy.